This invention relates generally to shaft assemblies and more particularly to a shaft assembly with recirculating ball roller joint unit.
Shaft assemblies including relatively axially movable inner and outer shafts have many different functions, one being the transmission of torque in an automotive steering column. In a typical steering column, the shaft assembly may connect a steering shaft of the steering column to a steering gear and is often referred to as an intermediate shaft. A slip joint is usually provided between the shafts to facilitate relative axial movement.
One requirement of the joint is that its resistance to relative axial movement, commonly referred to as xe2x80x9cslip loadxe2x80x9d, be kept to a minimum so that the shafts may be put together easily at the point of manufacture to speed up production without raising ergonomic concerns. A low xe2x80x9cslip loadxe2x80x9d is particularly important if the shaft assembly transmits torque as it is required to do when used with the steering column of an automotive vehicle. A low xe2x80x9cslip loadxe2x80x9d also facilitates collapse of the steering column in the event of a head on collision.
Customers are demanding lower and lower xe2x80x9cslip loadsxe2x80x9d. However, it has been difficult to meet these demands with designs currently available.
In accordance with the present invention, a recirculating ball joint is provided to facilitate relative axial movement between an inner shaft and an outer shaft and is especially designed for use with the steering column of an automotive vehicle. The ball joint includes a shell assembly secured within the outer shaft and defining recirculation races for balls which have a rolling engagement with the inner shaft.
Preferably the shell assembly includes two shells, with the shells respectively extending about opposite sides of the inner shaft and together extending around the entire periphery of the inner shaft.
Preferably each shell comprises a radially inner cage, a radially outer cage, and a ball retainer between the cages. At least one closed circuit race is provided for each shell. An inner cage groove and an outer cage groove cooperate to define a portion only of the closed circuit race, leaving open a remaining portion thereof. The retainer has a retainer groove which cooperates with a longitudinally extending groove in the inner shaft to define the remaining portion of the closed circuit race. The balls are adapted to circulate in the closed circuit race to facilitate axial movement of the inner shaft relative to the outer shaft. Preferably each shell has two such closed circuit races with balls circulating in each.
One object of this invention is to provide a shaft assembly with a recirculating ball roller joint having the foregoing features and capabilities.